240 
INSTINCT. 
Chap. VIT. 
are the most numerous; or that both large and small 
are numerous, with those of an intermediate size 
scanty in numbers. Formica flava has larger and 
smaller workers, with some of intermediate size; and, 
in this species, as Mr. F. Smith has observed, the 
larger workers have simple eyes (ocelli), which though 
small can be plainly distinguished, whereas the smaller 
workers have their ocelli rudimentary. Having care¬ 
fully dissected several specimens of these workers, I 
can afiSrm that the eyes are far more rudimentary in 
the smaller workers than can be accounted for merely 
by their proportionally lesser size ; and I fully believe, 
though I dare not assert so positively, that the workers 
of intermediate size have their ocelli in an exactly in¬ 
termediate condition. So that we here have two bodies 
of sterile workers in the same nest, differing not only in 
size, but in their organs of vision, yet connected by some 
few members in an intermediate condition. I may 
digress by adding, that if the smaller workers had been 
the most useful to the community, and those males and 
females had been continually selected, which produced 
more and more of the smaller workers, until all the 
workers had come to be in this condition; we should 
then have had a species of ant with neuters very nearly 
in the same condition with those of Myrmica. For the 
workers of Myrmica have not even rudiments of ocelli, 
though the male and female ants of this genus have 
well-developed ocelli. 
I may give one other case: so confidently did I ex¬ 
pect to find gradations in important points of structure 
between the different castes of neuters in the same spe¬ 
cies, that I gladly availed myself of Mr. F. Smith’s offer 
of numerous specimens from the same nest of the driver 
ant (Anomma) of West Africa. The reader will per¬ 
haps best appreciate the amount of difference in these 
